Purpose — determining the importance of sonographic and Doppler examination after 22 weeks of gestation for the diagnosis of obstetric and perinatal complications at pregnancy low risk.

Patients and methods. 4580 pregnant women from low risk subpopulation with normal results of ultrasound screenings. After 22 weeks of gestation sonographic and Doppler studies of pregnancy were performed. Perinatal outcomes of were studied as well.

Results. The incidence of pathological ultrasound changes after 22 weeks of gestation in women at low risk subpopulations was 9.8%. Сritical placental violations were found in 51/4580 women (1.13%). In early fetal growth retardation cases at 26–30 weeks of gestation (44/51 or 86.2%) the outcomes of pregnancies were unfavorable. In 83.9% cases of placental noncritical violations there were clinically favorable perinatal outcomes. In isolated polyhydramnios favorable outcomes were observed in 61.3% of cases. The risk of intrapartum distress after normal results of the III trimester ultrasound was high: OR 25 (95% CI 29–21), RR 83 (95% CI 77–88). The risk of premature rupture of membranes at normal results of the III trimester ultrasound was also high: OR 35 (95% CI 41–29), RR 88 (95% CI 94–80). Despite the low overall rate (2.5%) of identify of uterine artery Doppler changes more than half of women with such disorders had perinatally significant complications which were observed later. An important predictor of preeclampsia and perinatal complications in low-risk pregnancy can be considered a bilateral abnormal uterine artery Doppler in conjunction with early calcification of the placenta: OR 300 (95% CI 278–335), RR 75 (95% CI 71–79).

Conclusions. Features revealed by US in the second half of low-risk pregnancy in 3.2% of cases «translate» low'risk pregnancy into the high'risk, and in 6.6% — into the indefinite risk pregnancy. Medical tactics changed less than in 1% of the cases on the basis of ultrasound after 22 weeks of gestation in women at low-risk pregnancy. However, the value of third trimester ultrasound study is forecasting of negative or ambiguous outcome of pregnancy, direction at perinatal center, routine examination and treatment of newborns. Based on this analysis the inclusion of ultrasound scan at 26'30 weeks of gestation into antenatal care protocols may be considered reasonable.